Glad you found the problem, CRS!
Yes, this setting has caused me grief, not to mention it's the source of many "hey, this software doesn't work" complaints.
For normal dashcam use the "Always Auto-Fix Time Offset" setting should always be checked. It should only be unchecked in cases where the GPS data was collected separately from the movie. For example, if you use a GoPro for video and a separate GPS logger for navigation data. In that case you need to manually sync them up, so you don't want DV to attempt to auto-sync the time offset. Separate sources for video and GPS are common in the Unmanned Aerial System (UAS) community, where DV can also be used.
John
http://dashcamviewer.com